As is known, reactors are used to introduce reactance into a circuit. Generally, the function of a reactor is to control AC current. Three-phase line reactors have particular usefulness in adjustable-speed motor control applications and a known three-phase reactor 10 is shown in FIG. 1.
Three-phase line reactors, like the one shown in FIG. 1, are constructed from three coils of wire wound on bobbins. Each of the bobbins has a rectangularly-shaped main body 11 with first and second ends 12 and 13. Radially extending flanges 14 and 15 are positioned on each of the first and second ends 12 and 13, respectively, and wire is coiled between the two flanges. Thus, each bobbin holds a coil of wire which acts as an inductor. To enhance the performance of the wire coil, particularly its magnetic field characteristics, a magnetic material is often positioned in its hollow center as a magnetic core. One way of constructing a magnetic core in a bobbin wound with wire is to position a stack of flat metal sheets or laminations through the hollow portion of the bobbin. Often, but not necessarily, E-shape laminations (often called "E's") are used. Sometimes, bar-shaped laminations (often called "I's") are used. It is also common to use both E's and I's.
In reactors with three bobbins, the laminations are built up until they fill nearly the entire hollow center portion of each bobbin. When E's and I' are used, it is common to position the E's so that only the legs of each E are surrounded by the bobbins while the ends of each E are accessible and exposed. A stack of I's is positioned on the opposite side of the bobbins to complete the magnetic circuit. To firmly fix the E and I laminations in place, two metal support bars are inserted into each bobbin. Specifically, a first metal support bar 16 is inserted between the front wall of the bobbin and the top of the laminations and a second metal support bar 18 is inserted between the rear wall of the bobbin and the bottom of the laminations. Bolts 20 are inserted through bores in the metal support bars and the laminations and secured with nuts to tightly hold the laminations together and in place. Usually, two flanges (F and F') are bolted onto the ends of the metal support bars to provide a base on which the reactor stands.
One problem with the present method of constructing three-phase line reactors is the difficulty of aligning the components of the reactor before they are bolted together and maintaining that alignment during the bolting operation. As described above, numerous laminations must be stacked during the construction of the reactor and then these laminations must be fixed in position using several metal support bars. The support bars are manually aligned and bolted in place. Even when this process is carried out using a jig, the resulting reactor is often out of level, out of plumb, or both. Furthermore, the process of inserting and aligning the support bars is time consuming. Thus, the speed at which line reactors can be manufactured is limited. Metal support bars are also sources of eddy current losses in the reactor. Accordingly, it would be desirable to construct a line reactor without having to use metal support bars.